Water is a unique substance that can exist in three different states of matter. In its solid state, we call it ice, where water molecules are tightly packed in a crystalline structure. As a liquid, water molecules move more freely while staying close together. In its gaseous state, called water vapor, molecules move rapidly and spread out to fill available space.
Melting is the process where solid ice transforms into liquid water when heat energy is applied. As ice absorbs thermal energy, the rigid crystalline structure breaks down and molecules begin to move more freely. This phase transition occurs at zero degrees Celsius or thirty-two degrees Fahrenheit under standard atmospheric pressure.
Evaporation is the process where liquid water transforms into water vapor when sufficient heat energy is applied. As water molecules gain kinetic energy, they overcome intermolecular forces and escape into the gas phase. This phase transition occurs at one hundred degrees Celsius or two hundred twelve degrees Fahrenheit at standard atmospheric pressure. We can see bubbles forming as the water boils vigorously.
Condensation is the reverse process of evaporation, where water vapor transforms back into liquid water when cooled. As vapor molecules lose kinetic energy, they come closer together and form liquid droplets. During this phase transition, the energy that was absorbed during evaporation is now released back into the environment. This process is commonly observed when warm, humid air meets a cold surface.